Abstract:
By combining the chemistries of ultracapacitors and lithium-ion batteries, a company called Ioxus has created a hybrid energy-storage device that could recharge power tools in minutes and might never need to be replaced. The company says future incarnations could perhaps be used to capture energy from braking vehicles.

Ultracapacitors capture and release energy in seconds and can do so millions of times, but they store only about 5 percent as much energy as lithium-ion batteries. The hybrid can store more than twice the energy by volume of standard ultracapacitors. That's still much less than a lithium-ion battery, but the hybrid can be recharged quickly over 20,000 times as against a few hundred cycles for a typical battery.

A power tool using the lithium-ion ultracapacitor would run for only a 15th as long as it would on a battery but would recharge in just a minute. "Our product is for weekend warriors who don't use the power tool much every day" but want very fast charging, says Mark McGough, CEO of Ioxus. The company, which is based in Oneont, New York, already makes conventional ultracapacitors for hybrid-electric buses and for engine start-stop systems that are used to increase fuel economy in cars.